Senate Finance Committee Chairman Max Baucus said this morning that the committee would vote on Tuesday on an amendment to include a government plan in its version of the health care legislation.

The Finance Committee bill is the only Democratic bill in the House or Senate that does not include a government plan, a key provision for liberals.

At least three Democrats on the committee have expressed opposition to a government plan: Baucus himself, as well as Sens. Kent Conrad and Blanche Lincoln. Should the amendment get defeated as expected, we’ll have to see if any liberal Democrats still vote the plan out of committee. That may be an early indication of whether liberals will ultimately cave on the idea when it comes up for a vote in the Senate as a whole — i.e. if they literally face the choice between abandoning the government plan, or getting no health care bill at all.

Yesterday, Sen. Chuck Schumer, who is on the Finance Committee, insisted that the final legislation would include a “robust public option,” but his thinking was that it could be added on down the road, even if it doesn’t get passed at the committee level. Last week, Sen. Jay Rockefeller said he would vote against the bill at the committee level if it was not changed substantially from the original draft, and the lack of a government plan was his leading criticism of the legislation.

The Finance Committee will be debating amendments today until noon, and then recess until Tuesday. Monday is the Yom Kippur holiday.